1. Field of the Invention
The present invention relates to powered toothbrushes, and more particularly, to a toothbrush having a head with two distinct moving sections that each provide oral health benefits to the user.
2. Discussion of Related Art
Toothbrushes provide many oral hygiene benefits. For example, toothbrushes remove plaque and food debris to help avoid tooth decay and disease. They remove stained pellicle from the surface of each tooth to help whiten the teeth. Also, the bristles combined with the brushing motion massage the gingival tissue for stimulation and increased health of the tissue.
Powered toothbrushes have been available for some time. Powered toothbrushes have advantages over manual (non-powered) toothbrushes in that they impart movement to the bristles at much higher speeds than possible manually. They also may impart different types and directions of motion. These motions, generally in combination with manual movement of toothbrush by the user, provide superior cleaning than manual toothbrushes. Typically, powered toothbrushes are powered by disposable or rechargeable batteries that power an electric motor that in turn drives toothbrush head.
Known powered toothbrushes include a brush head with a bristle carrier portion that rotates, oscillates or vibrates in some manner so as to clean the teeth. The bristles, which typically comprise bristle tufts, are generally uniform with one end fixed into the bristle carrier portion and the other end free to contact the surface of the teeth while brushing. The free ends of the various tufts present a surface envelope that is capable of some deformation when the bristles bend. When in contact with the surface to be brushed, the bristles may deform so that the surface envelope tends to conform to the complex surface of the teeth. Human teeth generally lie in a “C” shaped curve within the upper and lower jaw, and each row of teeth consequently has a convex outer curve and a concave inner curve. Individual teeth often have extremely complex surfaces, with areas that may be flat, concave, or convex. The more precise conformation between the bristles and the tooth surface, the more effective toothbrush may be in cleaning, whitening and/or stimulating.
Known powered toothbrushes typically arrange the bristles in a compact conical or cylindrical pattern on a generally circular, disk-shaped bristle carrier. The powered toothbrush heads are traditionally compact, generally oval in shape and heads are produced with a flat trimmed bristle pattern. Alternatively, other head shapes and bristle patterns are available.
One example of a powered toothbrush is depicted in U.S. Pat. No. 5,625,916 to McDougall, which is hereby incorporated by reference in its entirety. Toothbrush shown in McDougall has a disc-shaped bristle carrier. The bristle carrier, and thus the bristles, are driven in a vibrating or oscillating manner. This type of toothbrush is described herein with reference to FIGS. 1A–1C. A toothbrush 5 includes a handle portion 10 at a proximal end of toothbrush 5 and a head 11 at a distal end of toothbrush 5. Handle portion 10 has compartments for containing a powered motor 14 and batteries 15 and 16. Head 11 includes a generally circular bristle holder (carrier) 13. A rotatable shaft 12 extends from the motor 14 to head 11. A shaft coupling 17 may be located along the shaft 12 and configured to provide for the shaft 12 to be separated at a point between the motor 14 and head 11. This permits the shaft to be removed from toothbrush 5, e.g., for cleaning, servicing, or replacement.
Head 11 includes a post 18 that provides a rotational pivot axis for the bristle holder 13 containing bristle tufts 19. The distal end of the shaft 12 has a journal or offset 20 that is radially displaced from the longitudinal axis of the shaft 12, which may be integrally formed therewith. The bristle holder 13 has a slot 22 that receives the offset 20. The offset 20 and slot 22 are configured so as to be oriented toward the intersection of the shaft 12 axis and the longitudinal axis of the post 18. When the motor 14 rotates the shaft 12, the motion of the offset 20 defines a circle about the shaft 12 axis and drivingly engages slot 22 such that the bristle holder 13 vibrates or oscillates about the post 18 axis through a rotational angle A. The rotational angle A is defined by the displacement of the offset 20 from the shaft 12 axis relative to the diameter of the bristle holder 13.
Although powered toothbrushes such as those described immediately above provide advantages over manual toothbrushes, they are subject to various limitations. Providing a rotating or oscillating bristle holder (carrier) with a typical oblong or oval toothbrush head constrains the size of the moving bristle holder, and consequently the area of bristles available for teeth cleaning. Also, when the bristles are placed in contact with the teeth during brushing, there is less bristle contact with adjacent areas, such as the gums. Thus, while these compact bristle patterns provide for cleaning, there is minimal whitening and stimulation.
One attempt to overcome the limitations associated with a small powered bristle area is shown in U.S. Pat. No. 6,000,083 to Blaustein et al. The toothbrush in Blaustein et al. has a bristle area and pattern similar to a manual toothbrush, but an area of the bristles has simply been replaced by a powered bristle section. The result is that the head has a powered or moving bristle section and static bristle section. The limitation of Blaustein et al. is that the static bristle section provides no better cleaning, whitening or stimulation than a manual toothbrush.
International Application No. PCT/EPO1/07615 of Braun GmbH discloses a powered toothbrush with two separate bristle parts that can move. Each bristle part can have a different range and/or type of motion. However, only one bristle part is powered. The other unpowered bristle part moves due to a resonance effect imparted by the frequency of the movement of the first bristle part.
This free resonance causes a number of difficulties. First, because any contact between the bristle parts will dampen or cancel any resonance of the unpowered bristle part, the unpowered bristle part “floats” separately from the powered bristle part. This necessitates separation or gaps between them. These gaps expose the internal workings of the head to foreign matter such as water, saliva, toothpaste, and food particles. This foreign matter may interfere with the workings of the unpowered bristle head. For example, the unpowered bristle part is spring-loaded to assist its resonance. Foreign matter may accumulate on or around the spring, interfering with its function. In addition, food particles may remain in the head and may fester and host microorganisms, which are undesirable if not potentially harmful when introduced directly into the mouth.
Another limitation of such a design is that movement of the unpowered bristle part may be damped by contact with the teeth, or lessened when the frequency of the powered part shifts from the resonance frequency. This can occur due to pressure imparted against the powered bristle part by the teeth or gums during brushing. Finally, the energy imparted to the unpowered bristle part is only a portion of the energy input into the powered part. Therefore, the unpowered bristle part is less effective in cleaning than the powered part, limiting the overall effectiveness of the toothbrush.
Thus, there is a need in the art for a powered toothbrush with increased effectiveness through a larger area of powered or driven bristles or bristles that are otherwise movable. There is also a need for a toothbrush having increased whitening and/or stimulation than known toothbrushes. There is further a need for such improved toothbrushes to be comparable in manufacturing and purchasing costs as known powered toothbrushes.